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# AE-May-2013-04-Bio-A4

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```National Exams May 2013
04-Bio-A4 - Biomechanics
3 hours duration
1. If doubt exists as to the interpretation of any question, the candidate is urged to include a
2. This is a CLOSED BOOK EXAM, with approved calculator allowed.
3. Five (5) questions constitute a complete exam paper.
4. Each question is of equal value.
5. Clarity and organization of the answers are important.
04~Bio-A4 Biomechanics
May 2013
Page 1 of7
(15 marks)
1.
Figure 1 shows an elderly subject of mass 60 kg exiting from a bath tub where the
right root contacts the ground and experiences a vertical ground reaction force
component of 400 N, a side-to-side force component of 45 N directed towards the bath
and a backwards force of 20 N. If these forces can be considered to act at the centre of
pressure, P, then
a)
Calculate the joint resultant moments at the knee and the hip joints in the sagittal
plane. Ignore inertial effects. (S marks)
b)
Calculate the joint resultant moments at the knee and the hip joints in the frontal
plane. Ignore inertial effects. (S marks)
c)
Calculate the joint resultant moments at the knee and the hip joints
transverse plane. Ignore inertial effects (S marks)
10
the
I
----&gt;,----II~-- ---
Figure 1
04-Bio-A4, Biomechanics
May 2013
Page 2 of7
(15 marks)
2.
Figure 2 below shows a link segment model of a person doing a one-armed handstand
on their right hand.
a)
Sketch the diagram of the kinematic chain A-8-C-D-E-F-G and give the number
of degrees of freedom for each of the joints that are within the chain (i.e. 11, 12 or
13). Also, label each of the relevant links in the chain (i.e. Ll, L2, L3, etc.) (5
marks)
b) Calculate the number of degrees of freedom in the entire kinematic chain (3
marks)
c)
Repeat b) for the case where both hands are on the ground (4 marks)
d)
Classify the chains in both b) and c) using two of the following four words: serial,
branched, open, and closed (3 marks)
)ru[fu
[:cJo---t-:~-&lt;l
Left Ann (LA) .........•.
lBJ
/
Right Arm (RA)
[E]
Left Forearm (LF)---+
[A] \
Left Hand
Figure 2
04-Bio-A4.
Biomechanics
May 2013
Page3 of7
(15 marks) 3. a) Provide short (1-2 sentences) definitions for the following terms (5 marks):
i)
ii)
iii)
iv)
v)
Flexion
Abduction
Ulnar deviation
Internal rotation
Varus angulation
b) What condition does the girl have in the photo below (figure 3, indicated by white
arrow)? (3 marks)
c) What muscles might be strengthened to correct this condition? (3 marks)
d) What musculoskeletal
disorders is this girl at risk for? (4 marks)
Figure 3
04-Bio-A4, Biomechanics
May 2013
Page 4 of7
(IS marks)
4.
A villain is kicking the base of a door in order to break it down (Figure 4). At the
instant of contact with the door, the toe decelerates with a value of 50 rn/s2
(tangential relative to the hip center) and the hip flexors have already relaxed to zero
action. The thigh and the lower leg segments are both 44 em long with centers of
mass halfway along that length. The masses of the thigh and lower leg segments are
7.2 kg and 4.3 kg respectively and their radii of gyration are 14 ern and 15 em
respectively.
Assume that the knee joint is flexed to 28 degrees and the ankle joint is in the neutral
position and that there is no relative motion or acceleration between the segments of
the leg.
a)
Draw the free body diagram of the entire leg (including all linear and angular
accelerations) and show all relevant dimensions. (5 marks)
b)
Draw the free body diagram of the entire leg showing all the relevant forces
and moments. (5 marks)
c)
Calculate the contact force between the door and the toe at the instant shown
assuming the hip joint to be not moving or accelerating linearly in any direction
(i.e. is fixed in space). (5 marks)
Figure 4
; ; } &gt;
04-Bio-A4, Biomechanics
May 2013
Page 5 of7
(15 marks)
5. Consider the x-ray in Figure 5 below. This is a frontal view of the right hip and thigh of
a 67 year old female complaining of pain and loss of weight-bearing in the right hip.
a) What injury has this person sustained (indicated by white arrow)? (4 marks)
b) Suggest a biomechanical mechanism by which this injury occurred (5 marks)
c) What surgical procedure should be used to correct this injury? How long do you
expect the healing process to take before return to full function? (4 marks)
d) Give two possible complications during the healing process. (2 marks)
04-Bio-A4, Biomechanics
May 2013
Page 60f7
Marking scheme
1.
2.
3.
4.
5.
15 marks
15 marks
15 marks
15 marks
15 marks
total;
total;
total;
total;
total;
04-Bio-A4, Biomechanics
a)
a)
a)
a)
a)
5,
5,
5,
5,
4,
b)
b)
b)
b)
b)
5,
3,
3,
5,
5,
c)
c)
c)
c)
c)
5
4, d) 3
3, d) 4
5
4, d) 2
May 2013
Page 7 of7
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